▎ 摘　　要

Owing to the large sizes involved, most calculations of the electronic properties of graphene and its fragments involve empirical tight-binding models restricted to nearest-neighbor interactions only. Such approaches fail to predict key electronic and magnetic properties, however, and rely on assumed geometries. While alternative approaches based on density-functional theory are much more successful in predicting properties, they are often computationally prohibitive to apply. We introduce a simple third-nearest-neighbor pi-only tight-binding approach that maintains the computational efficiency of the empirical method while achieving the accuracy of the density-functional methods to which it is parametrized. It yields both nuclear geometries and electronic structures of graphene fragments, providing an efficient and accurate replacement for traditional tight-binding models of graphene.